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Students in ecology (EES-152) at Lehigh University share pictures of our field activities via Twitter. Below are some highlights from a population ecology laboratory, which ended up being spread across two laboratory periods because we had to end early during the first period because of high winds.

The one red-backed salamander that my assistant and I found on our “pre-class” field trip, which was on a cold Saturday afternoon.

Would it be too cold for salamanders? After freezing temperatures on Friday night, my daughter and I took a brisk Saturday-afternoon hike through the Lehigh Experimental Forest. Our objective was to determine whether any red-backed salamanders (Plethodon cinereus) were under the nearly 100 coverboards that Michelle Spicer (Lehigh graduate student) and I had put out in preparation for this week’s Ecology (EES-152) lab.

We didn’t find any salamanders under the coverboards. Not a single one. However, after nearly an hour of searching (my assistant insisted that we not give up), we managed to recover a sluggish salamander from deep under a large rock. Salamanders were very abundant a couple weeks ago, but the sudden cold temperatures had clearly sent them digging deep in the soil, which is where they survive the winter. If only the cold snap had waited a few more days. Michelle and I had to quickly develop a backup plan for Monday’s lab.

However, we got lucky. Sunday was warm, and temperatures never dropped below the upper 50s during the night. Rain on monday morning and afternoon probably helped a bit too, and as far as I could tell, the students didn’t mind getting wet. Collectively, they counted 84 red-backed salamanders in approximately 2200 square meters of forest (almost 23,700 square feet). And that is a minimum estimate….we certainly missed some. So, scaling up, our estimate of red-backed salamander density, based on this single sampling effort a few days after the first freeze, was about 382 per hectare (or ~155 per acre). Therefore, there are likely well over 1000 red-backed salamanders in the Lehigh Experimental Forest. The numbers might seem surprising, but our estimate is lower than other estimates from eastern North America forests, where densities greater than 1000 individuals per acre have been observed. I suspect that if we had sampled a few weeks ago, our estimate would be much higher; in fact, I wouldn’t be surprised if there are more salamanders in the experimental forest than there are students at Lehigh University.

In addition to salamanders, the students collected information on the density of earthworms, using the liquid extraction technique. They will use the combined dataset, along with some additional observations and measurements, to test whether salamander and earthworm abundance differed between areas of the forest with deciduous (tulip poplar and sugar maple) and conifer (white pine) canopies. How might the type of canopy influence the abundance of earthworms? How might it influence the abundance of salamanders? Or perhaps the forest vegetation doesn’t matter at all? Hypotheses?